Punching die



Dec. 23, 1952 J, KQPCZYNSKI 2,622,682

PUNCHING DIE Filed May 51, 1946 Patenten] Dec. 23, 1952 UNITED STATES ?ATENT OFFICE PUNCHING DIE John F. Kopczynski, Buffalo, N. Y.

Application May 31, 1946, Serial N0. 673,713

. 1 Clai m.

This invention relates to too1s and partielllarly to punches for punching ho1es or apertures in sheets.

In punching apparatus the punch element has a reduced end portion er stem which does the punching, and an intermediate 01 junction part connecting the main body portion with the reduced end portion or punching end. Thi intermediate part increases progressively in cross sec.tional area through a plurality of stages from the reduced end to the body portion. Considerab1e diificulty has been experienced with punch elements cf this type, owing to the fast that the reduced end portion frequently :breaks -off at approximately its junction with the intermediate part. The cause of such breakage is due to a whipping of the reduced end of the punch element, caused by the stresses created in the actual punching operation. When such a breakage oceurs, the punch must be replaced by a new punch which in itself is a substantial expense, and also causes delay whi1e the punch element is being replaced and aiigned.

An object of this invention is to provide an improved punch device or tool; with Which punching operations may be performed in the usual manner; with which breakage and wear of the punch element are substantially reduced 01 eliminated; which Will not interfere with the usua1 operations :of the tool; with which the initial cost of the 13001 will be relatively sma1l; and which will be prac-tical and relatively simple,

Another object of the invention is to provide an improved punch element with a ground surface on the punching end, in which the ground grain runs parallel to the longitudinal axis 0f the end; with which the picking up of small particles of stock by the reduced punch end Will be reduced 130 a minimum; with which the tendency of the punch element to crack and break will be reduced; with which a more perfect blending between the reduced end and tapered portion may be obtained; with which heating of the punch during grinding is reduced; and Which will-be relatively simple, practical, inxpensive, and of long 1ife.

Another object is to provide an improved and simple punch assembly in which the punch element will be guided in the stripper ab a position remote from its advance, punching end; with which wear in -the guide Will be reduced to a minimum; and with which guides for the punch element may be interchangeably mounted in the stripper for use in guiding different sizes of punch elements.

Another object is to provide improved and simple means for securing a gide sleeve on a punch element, With which the sleeve will be securely anchored to said element against forces created during punching operations and tending uo displa-ce said sleeve along the punch element.

Another object is provide an improved and simple method of grinding-the sides of a punch element to reduce it accurately to the desired size, and 130 form thereon a ground grain running parallel to the longitudinal axis of the punching end o1 the punch element; and with Which one may obtain a more perfect blending or merging of the punching end into the tapered section connecting the punching end to the body of the punch eiement.

Other objects and advantages will be apparent from the following description of one embodiment of the invention, and the nove1 features will be particularly pointed out hereinafter in sonnection with the appended ciaim.

In the accompanying drawing:

Fig. 1 is a sectionai elevation 0f a punch assembly constructed in accordance with this invention;

Fig. 2 is a sectional plan of a pa1't 0f the same, the section being taken approximately along the line 2-2 of Fig. 1;

Fig. 3 is an elevation of the lower part of the punch element, with a diagram illustrating the improved method of grinding the punching stem and adjoining tapered section of the punch element; and

Fi'. 4 is a sectional' elevation cf the sleeve or collar to be mounted on the punching element.

In the illustrated embodiment; of the invention, a punch element l is suitably but detaehab1y mounted in a die head 2 which move tovvards and from a die base 3 having a female die opening 4 a1ong its upper surface, with a downwardly enlarging passage 5 conneoted to the opening 4 for the discharge of slugs. The punch element I has its base 0r body part mounted in the head 2 in any suitable manner, such, for example as disciosed in my Patent N0. 2329061 and in my copending application for patent Sei. N0. 595,318 filed May 23, 1945,

The punch element l carries a punching end or stem 6 which has a size and shape to pass through the opening 4, with a proper clearance, for piercing a blank or stock 1 0f meta.l or any other suitable sheet material. This punch end 6 is j-oined to the body part of the punch element by a tapered transition part 8 (see Fig. 3) which has i-ts smaller end merging into it's piercing end is known as a pressure stripper.

3 6. A sleeve or collar on the punch elemeint 9 is provided with a tapered, interior passage II merging a1; one end into a straight passage section II having the shape of the punching end 9 and a size to have a presg fit; therewlth. The tapered part I of the passage fits I;he tapered part 8 of the punch element rather snugly. A pin I2 extendg transversely through the sleeve 9 and the tapered transition part 8 of the punch element While the sleeve ls snugly fitted on the punch element against tapered p2ut 8. This pln I2, supplementing the press fit, positively locks the sleeve on the punch element and resists end wise pulls on the sleeve tending 120 dislodge it from its fitting engagement against; the taperecl surface of the part 8 of the punch elemenb.

A stripper member I3 disposed above the blank I, is either directly carried by the base 3 or preferably, as shown is carried by rods I4 and springs I5 on the die head 2 and forms what Thls invention is not concerned with whether the stripper member I3 is carrled by the die head 2 as a pressure stripper, or rigidly on the base, both being well known types of mounting for the stripper member. The stripper member I3 is, however, provided with a, passag'e I4 which snugly fits ehe punching end 6 of the punch element, and through which this punching end 6 is adapted to move during a punching operation. Thls snug, sliding fit between the punching end 6 of the punch element and the passage I4 is preferably along the lower edge of the stripper member, so as 110 give support to the punch end of the punch elernent as closely as possible to the blank I being perforated. The stripper member I3 also has a larger passage I5 above passage I4 in which the sleeve 9 snugly and slidingly fits during the punching operation, so as to guide anal support the punch element at; the junction of the punching end with the tapered part 8 of the punch element.

Any whipping o1 the punching end 6 of the punch element is avoided by the engagement of the collar or sleeve 9 with the side wall of the passage I5, and the passage I5 is deep enough to enable ehe punch 130 make its full stroke before the sleeve 9 reaches the bottom of 'the passage I5. This guiding support for the punch efiectively reduces or largely ellminattes the breakage of the punch heretofore experienced, am]. for the first time makes lt possible to pierce blanks of greacer thickness than the diameter of I:he piercing t001. The periphery of the s1iae've or collar 9 is machined to its proper size, p1ef erably the same diameter as that of the main body of the punch element.

While the punch element in the drawing is illustrated a s formed 130 pierce round apertures in the blank 0r work sheet, and the 0011211 or sleeve 9 has a circular periphery, lt will be understood that either 01' both of th'e punchlng end of tne punch anal the sleeve 9 may have non-circular peripheries of any particular design, depending upon the character of the aparture to be punched in the blank or work. The passages in the stripper in which the punching end of the punch element anal the sleeve 9 reciprocate, Will always, of course, confonn in character or shape to the character or shape of ehe surface of the punching end and sleeve. With I:he punch element; reenfo'rced by the sleeve 9 slidingly guicled in thls manner, it has been possible to successfully punch apertures in blanks having a t hickness more than twice the diameter of the punch or aperture, and du so in production for long periods of time without requiring re-grinding the punch element.

Inasmuch as the punch element is usually hardened before the sleeve 9 is applied thereto, lt is preferable to form a transverse passage I'I in the tapered part 8 of ehe punch element, before the punch element is hardened. When the sleeve or collar 9 is to be applied, the hardented punch element is mounted in a drill press, but not rotating, with the drlll in the passage I'I, and then while the punch element remains anchored in that position and not rotating, the drill is wlthdrawn from the passage I'I, the collar or sleeve 9 applied over the punch el'ement with a press fit, and then the drill brought down while rotating to drill a hole in the sleeve 9 which will be in perfect alignment with -the passage I'I. 'I'he drill is then withdrawn and the dowel 0'1' coupling pin I2 passed through the aligned passages in the sleeve 9 and tapered part 8 of the punch element. In this way it is practical to harden o1 temper the punch element after the passage II is formed and before the s1eeve 9 is applied.

'Ihe sleeve 9 is preferably made of bearing metal, such as bearing bronze, and it has been found that in such ca;ses wear is reduced between the sleeve and the passage I5 in the stri1aper I3. Bearing metals such as bearlng bronze are considerably softer than the t001 steel of Which the punches a1e made and the too1 steel is tempered to harclen it. 'I'he relatively soft metal on the surface la'yer of the sleeve or the entire sleeve When made of soft metal acts as a damper to damp vib1ations of the punch. When a punch engages a sheet metal blank at the instant he pierclng of the blank starcs ehe impact is rather heavy, and this sets up a lateral vibration on the punch which tends to snap the punch and cause molecular fatigue of the punch ab the junction of the tapered part of the punch and the punching end. The softer metal absorbs and damps these vibrations so as to greatly reduce the breakage of the punches. The thicker the metal of the blank, the greater ehe impact and, consequently, the greater the vibration tendency of the punch. A piece of 1ubber or soft material on a prong of a tuning fork will absorb the vibrations or damp them, and this soft metal appears to damp or absorb the vibrations of the punch, and therefore, it is possible to increase the thlckness of the sheet meta1 which can be successfully pierced by a punch. Preferably the guide passages in the stripper I3 for the punch element are provided in a separate sleeve or member I9 which is removably secured in an aperture in the stripper I3, so that When different size punches are interchangeably placed in the die head 2, a suitably formed liner I9 having passages I4 and I5 fitting those of the punching end 6 0f the punch element and the periphery of the sleeve 9 may be inserted in the strlpper I3. If desired, the liner I9 may be made of bearing metal, in which event the sleeve 9 may also be made either of bearing metal er hardened steel 01' other material.

It is also desirable in punches which have a ground punching end, to have I3he ground grain on the periphery of the punching end of the punch element run lengthwise of the punch element. Heretofore the ground grain, that is, the grain surface produced by grinding, extended peripherally around the punch elemenp because the grinding usua1ly occurred by rotating the punch element. In such cases, tha cross ground grain tended to pick up small pieces of stock and bind in the blank and. female die. In Fig. 3 is illustrated diagrammatically an improved method 01 grinding the punching end 6 of a punch element in a manner to have ehe ground grain run lengthwise of the punch e1ement, to avoid having the punch element pick up pieces of stock, and to have the punching end b1end easily into the tapered part 9.

Referring now to Fig. 3 in which the grinding action is shown diagrammatically, it will be understood that the punch element I is mounted. in the usual lathe chuck for rotation about 1ts axis, as usual in grinding such punches heretofore and on the tool stock (not shown) of the 1athe carriage, is mounted a grinding wheel 20, the spindle 21 of which is vertical, that is With it's axis in a. plane which parallel 1:0 the axis of rotation cf the punch e1ement but offset therefrom. This spindle 21 being mounted on bhe 12001 stock is first shifted by movement of the too1 stock until the grinding whee1 29 engages the periphery of the punching stem of the punch element. While the punch element 6 is rotating very slowly With the chuck of the 1athe, the grinding wheel 211 is independently rotated at high speed with the spindle 21 and slowly shifted, by travel of the 1athe carriage along line AA parallel to the axis of the punch element, t0 grind the punch end to the desired size. After the 12001 stank has been moved with the carriage along the 1athe bed until the grinding wheel reaches the desired junction between the punching stem and the tapered part 8, the travel of t-he car-riage is ended.

While the carriage of the lathe mounting the 11001 stock remains, in this position, the top part of the 12001 stock which mounts the grinding whee1 spindle 2l is on the carriage ab an angle to the axis of the punch in the direction of the 1ine BB, Which is parallel to the tapered edge 8 of the punch e1ement. During this movement ooth the grinding whee1 20 am]. the punch element are rotating a1; the same time, which grinds the desired taper 8 on the punch element with a very caref-u1 and accurate blending between the straight section of the punching end and the tapered par1: of the punch element. Ehe sma11 surface of contact between the grinding whee1 and the punch element reduces heating of the punch element to a minimum. Because of the high speed of the grinding wheel in relation to the slow rotation of the punch element I, the ground grain runs substantially lengthwise of the element l.

I1; will be understood that various changes in ehe details, materials and arrangements of parts, Which have been herein described and illustrated in orc1er 1:0 explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention, as expressed in the appended c1aim.

I claim:

A tool comprising a, body portion, a convergingly tapered portion on one end of the body portion, and a cylindrical punching end p0rtion, of uniform cross sectional area along its length, forming an extension of the smaller end of said tapered portion and merging into said tapered portion in a concave curve, said punching end portion having a, ground peripheral surface continuous throughout said end portion and up the smaller end of the tapered portion, Wih the ground grain of that surface running in a direction lengthwise 01 said punching end and tapered portions, a sleeve having a passage fitting and telescoping snugly with the full length of said tapered portion anal With a substantial and adjacent part of said punching end portion, and a meuhanical interlock between said sleeve and punch to secure said sleeve against endwise movemenl: an the tapered portion.

JOHN F. KOPCZYNSKI.

REFERENCES CITED 'Ihe following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,115908 Fox May 3, 1938 2213767 Markwick Sept. 3, 1940 2,318837 Connor May 11, 1943 2323'756 Smith Ju1y 6, 1943 2,380123 Smith Ju1y 10, 1945 2419529 Braaten Apr. 29, 1947 2431567 Kopczynski et a1. Nov. 25, 1947 FOREIGN PATENTS Number Country Date 195,901 Great Britain Apr. 12, 1923 

